cell mediated immunity Flashcards
what is the immune response mediated by
T lymphocytes
where do lymphocytes migrate or derive from?
thymus
what happens once the lymphocytes migrate to the thymus
the mature into T lymophocytes
when lymphocytes mature into t lymphocytes where do they next migrate to
to the lymphoid tissues
how do you tell the difference between T lymphocytes
each one expresses different surface proteins (known as the clusters of differentiation)
what type of CD molecules do early T cells have
CD4 - CD8
what main CD molecule do T helper cells present
CD4+
what do T helper cells secrete
cytokines (acting as messenger molecules)
what do cytokines stimulate
B cells and macrophages
what stimulates proliferation and differentiation of T cells esp. CD8+ CTL
cytokines secreted from T helper cells
are Th1 or Th2 cytokines anti-inflammatory or proinflammatory
Th1- proinflammatory
Th2 - anti-inflammatory
what do Th1 cytokines trigger
cell mediated immunity and phagocyte dependant inflammation
what do Th1 cytokines target
intracellular parasites
what is the main Th1 cytokine
IFN-y
what do Th2 cytokines inhibit
phagocytosis independent inflammation
does Th2 increase or decrease with tumour presence
increase
what type of CD molecule do cytotoxic T cells express
mainly CD8+
how do cytotoxic T cells kill cells
with intracellular microbes which produce foreign antigens
what happens once the cytotoxic T cells are activated
cytotoxic granules are released into the target - ensuring specific kills and reduces collateral damage
what is perforins role in cytotoxic t cells killing cells
it builds pores in the membrane for entry
what is Granzyme A’s role in cytotoxic t cells killing cells
activates ssDNA breaks, caspase independent apoptosis (programmed cell death)
what is Granzyme B’s role in cytotoxic t cells killing cells
activates caspase cystine proteases to initiate caspase dependant apoptosis
what is regulatory T cells role in the immune system
inhibits the immune response, to maintain homeostasis
has a role in preventing allergy and hypersensitivity
has a role in transplant tolerance
what do natural killer T cells share surface markers with
immune NK cells and cell mediated T cells
what type of CD molecules do natural killer T cells express
CD16+ (they recognise IgG coated pathogens
what is natural killer T cells role in the immune response
- surveillance and clearance of tumour cell (by increasing stress induced ligands)
- maintains self tolerance and regulates autoimmune diseases
what is the role of CD3
co-aids in activating CD8+ and CD4+
where are CD3 molecules found in high percentage
peripheral T cells
where is the CD45 marker expressed
on almost all leucocytes
what do CD45 molecules do
they activate and supress lymphocytes
- and have a role in T cell maturation
what are APC’s
antigen presenting cells
what do APC’s do to aid the immune response
they capture and display antigens to activate T lymphocytes
what is the first stage of APC’s capture and display of antigens
1- bacterium is engulfed by phagocytosis into a dendric cell and is encased into a phagosome
what is the second stage of APC’s capture and display of antigens
lysosomes fuse with the phagosome and digest the bacteria
what is the third stage of APC’s capture and display of antigens
immunodominant epitopes are associated with MHC II and are presented on the cell surface
what do APC’s include
dendritic cells, macrophages, B cells
what are costimulators
molecules on APC’s that function together with antigens to activate T cells
what does MHC stand for
major histocompatibility complex
what is a MHC
a group of genes that code for cell surface histocompatibility antigens
what do MHC’s do
they help anchor the antigen on the external surface of the APC
what is required for the activation of naïve T cells
the recognition of MHC
where are class 1 MHC’s expressed
on virtually all nucleated cells
where are class 2 MHC’s expressed
dendric cells, B cells and macrophages
what does polygenic mean
has several different class 1 and class 2 genes with similar functions
what does polymorphic mean
has multiple variants of each type within the whole population
what are MCH’s that can only be found in humans known as
HLA’s (human leukocyte antigens)
what are class 1 encoded by (in terms of HLA)
HLA-A, HLA-B, HLA-C
what are class 2 encoded by (in terms of HLA)
HLA-DR, -DP and -DQ
